Islam condemns lying. If lying is originally forbidden, then April Fools’ would consequently be forbidden because of the unwarranted dismay and chagrin it causes, even if it is for just one hour.
According to the dictionary, April Fools’ Day is a day for practical jokes, but in many places those jokes take the form of lies.
Islam condemns lying. Good people, in general, consider it a vice. If lying is originally forbidden, then April Fools’ would consequently be forbidden because of the unwarranted dismay and chagrin it causes, even if it is for just one hour. It plays with people’s trust, and is a pure emulation of vice.
Moreover, telling lies is bad conduct. It is not proper for righteous people and true believers; rather, it is a sign of hypocrisy, as the Prophet (peace and blessings be upon him) said, “The hypocrite has three characteristics: he tells lies, breaks his promise, and breaches the trust.” (Al-Bukhari and Muslim)
The Prophet (peace and blessings be upon him) warned against lying for the purpose of entertaining people. He said, “Woe on anyone who speaks to entertain the people by lying, woe on him, woe on him…” (Abu Dawud, At-Tirmidhi, and An-Nasa’i)
The Prophet (peace and blessings be upon him) also said, “One is not considered a true believer till he abandons lying for fun and arguing even if he was telling the truth.” (Ahmad and At-Tabarani)
Several Prophetic hadiths warned the Muslims against frightening others seriously or jokingly. The Prophet (peace and blessings be upon him) is reported to have said, “It is not permissible for anyone to frighten a Muslim.” (Abu Dawud)
Consequently, lying is forbidden in any form, and on this occasion (April Fools’ Day) it is forbidden for four reasons:
1- The prohibition of lying which is confirmed by the Quran and the Sunnah.
2- The unwarranted grief or fear it may bring on a person or his entire family, even if only for one hour.
3- The betrayal of trust it entails
4- The emulation of a silly custom that is not ours, that of lying.
Sometimes the idea of telling a lie on this day may be obnoxious to the whole society, not only to a person.
Courtesy: About Islam